Metallic alloy nanocomposite for high-temperature structural components and methods of making

ABSTRACT

A nanocomposite comprising a plurality of nanoparticles dispersed in a metallic alloy matrix, and a structural component formed from such a nanocomposite. The metallic matrix comprises at least one of a nickel-based alloy and an iron-based alloy. The nanocomposite contains a higher volume fraction of nanoparticle dispersoids than those presently available. The structural component include those used in hot gas path assemblies, such as steam turbines, gas turbines, and aircraft turbine. A method of making such nanocomposites is also disclosed.

BACKGROUND OF INVENTION

The invention relates to a nanocomposite comprising a plurality ofnanoparticles dispersed in a metallic alloy matrix and structuralcomponents comprising such nanocomposites. More particularly, theinvention relates to method of making such nanocomposites.

The continuing effort to design and build more powerful and moreefficient turbo-machinery, such as gas turbines, steam turbines, andaircraft engines, requires the use of materials having enhanced hightemperature performance capabilities. Such performance enhancementsrequire state-of-the-art materials with vastly improved mechanicalproperties such as strength and creep resistance.

High temperature structural materials can be strengthened in a number ofways such as, for example, grain refinement, solid solutionstrengthening, precipitate strengthening, composite strengthening, anddispersoid strengthening. One method of strengthening alloys calledOrowan strengthening incorporates a fine distribution of hard particlesinto a metallic alloy matrix. Orowan strengthening depends upon theformation of an array of dispersoid particles that serve as obstaclesfor impeding dislocation motion within the alloy matrix. The strength ofthese particle-reinforced alloys is inversely proportional to thespacing between these particles, which can be controlled in turn bycontrolling the size of the dispersoid particles. Thus, the use ofnanoparticles as dispersoids offers the potential of substantiallyenhancing alloy strength.

The introduction of hard dispersoid nanoparticles during the processingof the nanodispersoid-reinforced alloys presents a technical challenge.Current processes to disperse particles include powder metallurgyroutes, such as mechanical alloying of micron-sized particles, incombination with secondary processes, which include hot-isostaticpressing and thermomechanical processing by hot-forging or extrusion. Inthe mechanical alloying process, nanoparticles are created by repeatedfracture of the micron-size dispersoid particles during milling. Whilethis is a well-established process for oxide-dispersion strengthened(ODS) alloys in iron- and nickel-based alloys (such as, for example,Inconel MA alloys), the process fails to produce a homogeneous ofdistribution of the particles in the alloy matrix, especially for largecomponents. In addition, the loading of the particles in the alloycomposites produced by this process is typically limited to less than 2%by volume.

Current processes are unable to produce alloy nanocomposites havingsufficiently high loadings of nanoparticles. Therefore, what is neededis an alloy nanocomposite in which dispersoid) nanoparticles arehomogeneously distributed throughout the metallic alloy matrix. What isalso needed is an alloy nanocomposite having a sufficiently high loadingof dispersoid nanoparticles having high temperature performancecapabilities that adequate for use in hot gas path assemblies, such asturbine assemblies. What is further needed is a method of making alloynanocomposites having high loadings of dispersoid nanoparticles, whereinthe dispersoid nanoparticles are homogeneously distributed throughoutthe alloy nanocomposite.

BRIEF SUMMARY OF INVENTION

The present invention meets these and other needs by providing ananocomposite comprising a plurality of nanoparticles dispersed in ametallic alloy matrix, and a structural component formed from such ananocomposite. The nanocomposite contains a higher volume fraction ofnanoparticle dispersoids than those presently available. Thenanocomposite may be used to fabricate structural components, such asthose used in hot gas path assemblies, such as steam turbine, gasturbine, and aircraft turbine. The present invention also discloses amethod of making such nanocomposites.

Accordingly, one aspect of the invention is to provide a structuralcomponent used in a hot gas path assembly comprising a nanocomposite.The nanocomposite comprises: a metallic matrix; and a plurality ofnanoparticles dispersed throughout the metallic matrix, wherein theplurality of nanoparticles comprises from about 4 volume percent toabout 30 volume percent of the nanocomposite.

A second aspect of the invention is to provide a nanocomposite. Thenanocomposite comprises a metallic matrix and a plurality ofnanoparticles dispersed throughout the metallic matrix. The plurality ofnanoparticles comprises from about 4 volume percent to about 30 volumepercent of the nanocomposite and is formed by a thermomechanical processfollowed by severe plastic deformation.

A third aspect of the invention is to provide a structural componentcomprising a nanocomposite. The nanocomposite comprises: a metallicmatrix, wherein the metallic matrix comprises at least one of anickel-based alloy, an iron-based alloy, and combinations thereof; and aplurality of nanoparticles dispersed throughout the metallic matrix. Theplurality of nanoparticles comprises from about 4 volume percent toabout 30 volume percent of the nanocomposite, and the nanocomposite isformed by a thermomechanical process followed by severe plasticdeformation.

A fourth aspect of the invention is to provide a method of making ananocomposite. The nanocomposite comprises a metallic matrix and aplurality of nanoparticles dispersed throughout the metallic matrix,wherein the metallic matrix comprises at least one of a nickel-basedalloy, an iron-based alloy, and combinations thereof, and wherein theplurality of nanoparticles comprises from about 4 volume percent toabout 30 volume percent of the nanocomposite. The method comprises thesteps of: providing a nanocomposite powder, wherein the nanocompositepowder comprises a plurality of nanoparticles and a metallic matrixmaterial; consolidating the nanocomposite powder; and thermomechanicallyprocessing the nanocomposite powder to form the bulk nanocomposite.

These and other aspects, advantages, and salient features of the presentinvention will become apparent from the following detailed description,the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a transmission electron microscopy (TEM) image of ananocomposite of the present invention;

FIG. 2 is a flow chart illustrating the method of making a nanocompositeaccording to the present invention; and

FIG. 3 is a scanning electron microscopy (SEM) image of a nickel-basedalloy nanocomposite powder of the present invention containing 5 volumepercent yttrium oxide.

DETAILED DESCRIPTION

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that terms such as “top,” “bottom,”“outward,” “inward,” and the like are words of convenience and are notto be construed as limiting terms.

Referring to the drawings in general and to FIG. 1 in particular, itwill be understood that the illustrations are for the purpose ofdescribing a preferred embodiment of the invention and are not intendedto limit the invention thereto. FIG. 1 is a transmission electronmicroscopy (TEM) image of a nanocomposite 100 of the present invention.Nano composite 100 comprises a metallic matrix 110 and a plurality ofnanoparticles 120 dispersed throughout the metallic matrix 110. Theplurality of nanoparticles 120 comprises from about 4 volume percent toabout 30 volume percent of nanocomposite 100. In particular, FIG. 1shows a nanocomposite 100 in which metallic matrix 110 comprises anickel-based alloy and plurality of nanoparticles 120 comprises yttriumoxide (Y₂O₃). In the sample shown in FIG. 1, the yttrium oxidenanoparticles comprise about 5 volume percent of nanocomposite 100.

Metallic matrix 110 comprises at least one of a nickel-based alloy, aniron-based alloy, and combinations thereof. Non-limiting examples ofsuch nickel-based alloys that may be used to form metallic matrix 110include Ni—Cr based alloys, Ni—Cr—Al based alloys, and combinationsthereof. Iron-based alloys that may be used to form metallic matrix 110include, but are not limited to Fe—Cr based alloys, Fe—Cr—Al basedalloys, and combinations thereof.

The plurality of nanoparticles 120 comprises at least one of aninorganic oxide, an inorganic carbide, an inorganic nitride, aninorganic boride, an inorganic oxycarbide, an inorganic oxynitride, aninorganic silicide, an inorganic aluminide, and combinations thereof.Inorganic oxides that may comprise the plurality of nanoparticles 120include, but are not limited to, yttria, alumina, zirconia, hafnia, andcombinations thereof. The inorganic carbides that may comprise theplurality of nanoparticles 120 include, but are not limited to, carbidesof hafnium, tantalum, molybdenum, zirconium, niobium, chromium,titanium, tungsten, and combinations thereof.

In one embodiment, each of the plurality of nanoparticles 120 issubstantially spherical in shape. In other embodiments of the invention,each of the plurality of nanoparticles may be rods, needles, spheroidalshapes, and the like. Alternatively, plurality of nanoparticles 120 maycomprise a mixture of nanoparticles having a variety of such shapes.Each of the plurality of nanoparticles has at least one dimension thatis in a range from about 10 nm to about 500 nm. In one embodiment, adimension of each one of the plurality of nanoparticles 120 is in arange from about 10 nm to about 30 nm.

One method of strengthening of alloys is a mechanism known as Orowanstrengthening, in which a fine distribution of hard particles isincorporated into an alloy. In this strengthening mechanism, an array ofsuch dispersoid particles impedes dislocation motion. The strength ofsuch particle-reinforced alloys is inversely proportional to the spacingbetween the dispersoid particles. Spacing of the dispersoid particlescan, in turn, can be controlled by controlling the size of thedispersoid particles. For a given volume of dispersoid particles, usingdispersoid particles with sizes in the nanometer range can decreasespacing and thus substantially enhance alloy strength.

Currently, powder metallurgy routes in combination with secondaryprocesses, such as mechanical alloying processes, are used to disperseparticles. In the mechanical alloying process, nanoparticles are createdby repeated fracture of micron-size dispersoid particles during milling.Such processes fail to achieve a homogeneous particles distributionwithin the alloy, particularly for large components. In addition, theloading of the particles in the alloys formed by such processes istypically limited to less than 2% by volume.

Accordingly, the nanocomposite 100 provided by the present inventionovercomes the loading and dispersion limitations encountered withcurrent dispersoid strengthened alloys. The invention provides ananocomposite 100 with superior mechanical properties achieved throughdispersoid strengthening by a providing a higher volume fraction ofnanoparticle dispersoids than those presently available. The pluralityof nanoparticles 120 comprises from about 4 volume percent to about 30volume percent of nanocomposite 100. In one embodiment, the plurality ofnanoparticles 120 comprises from about 10 volume percent to about 30volume percent of nanocomposite 100.

The higher volume loadings of the plurality of nanoparticles 120 of thepresent invention provide nanocomposite 100 with mechanical propertiesthat are superior to those of current state-of-the art materials.Nanocomposite 100 also exhibits greater microstructural stability atelevated temperatures, allowing strength and creep resistance toretained at much higher temperatures than those provided by currentoxide dispersion strengthened (ODS) alloys. Nanocomposite 100 isthermally stable up to about 1200° C.

As described herein, the nanocomposite 100 of the present invention maybe formed into high-temperature structural components for use in hot gaspath assemblies, such as steam turbines, gas turbines, and aircraftengines. Such components include, but are not limited to: rotatingcomponents, such as turbine airfoils and turbine disks; staticcomponents, such as ducts, frames, and casings; combustors; and thelike. Forming techniques, such as powder metallurgy techniques,thermomechanical processing, and the like, that are well known the art,can be used to form nanocomposite 100 into the desired structuralcomponent.

In addition to nanocomposite 100 and a structural component made fromnanocomposite 100, the present invention also provides a method ofmaking nanocomposite 100. A flow chart illustrating the method 200 ofmaking nanocomposite 100 is shown in FIG. 2.

Referring to Step 210 in FIG. 2, a plurality of nanoparticles 120 isfirst combined with a metallic matrix material, such as, for example, analloy powder, to form a nanocomposite powder. In one embodiment, thenanocomposite powder is produced by blending at least one metallic alloypowder with a predetermined volume fraction of hard dispersoidnanoparticles. Each of the dispersoid nanoparticles has at least onedimension ranging from about 10 nm to about 500 nm. Techniques, such as,mechanofusion, mechanical alloying, cryomilling, and the like, are usedseparately or in combination with each other to form the nanocompositepowder. Such methods, particularly mechanofusion and cryomilling, act tocoat and surround individual particles of the metallic alloy powder witha plurality of dispersoid nanoparticles. A SEM image of a nickel-basedalloy nanocomposite powder, containing 5 volume percent yttrium oxide,of the present invention is shown in FIG. 3.

In one embodiment, the nanocomposite powder is produced by in-situformation of a plurality of nanoparticles 120 within an alloyed metallicmatrix 110. This is achieved by cryomilling micron-sized particles ofthe metallic alloy matrix material in a reactive atmosphere, comprising,for example, at least one of nitrogen, and a hydrocarbon, such as, butnot limited to, methane. The gases present in the reactive atmospheremay additionally serve as the coolant for cryomilling. Alternatively,cryomilling may be performed in an inert atmosphere that comprises, forexample, at least one of argon and helium.

The cryomilling feedstock comprises at least one alloyed metal powderthat comprises at least one metallic element. The at least one metallicelement may be either reactive or refractory in nature. Such metallicelements include, but are not limited to, Al, Cr, Ti, Mo, Nb, Ta, W, B,Zr, Hf, Ta, combinations thereof, and the like. The plurality ofnanoparticles 120 comprising the metallic elements is formed bycryomilling such metallic alloys. The cryomilling action separateshighly reactive nanosize particles from the micron-size particles ofmetallic alloy matrix material. When cryomilled in a reactiveatmosphere, the metallic nanoparticles react with the reactive gases toform hard dispersoid nanoparticles, such as oxides, carbide, nitrides,combinations thereof, and the like. The hard dispersoid nanoparticlessurround each of the micron-size particles of metallic alloy matrixmaterial to achieve the fine distribution incorporation that is neededfor Orowan strengthening.

The nanocomposite powder is then consolidated (Step 220) andthermo-mechanically processed (Step 230) to form a bulk dispersoidnanoparticle-reinforced metallic alloy nanocomposite 100. Consolidationof the nanocomposite powder (Step 220) into a compact is performed usingtechniques, such as cold pressing, hot pressing, forging, extruding,canning, and the like, that are known in the metallurgical arts. Step230 is carried out using techniques such as, but not limited to,forging, hot-extrusion, and hot-rolling, either separately or incombination with each other. In another embodiment, dispersoidnanoparticle-reinforced metallic alloy nanocomposite 100 is formed fromthe consolidated nanocomposite powder compact by subjecting thenanocomposite powder compact to severe plastic deformation. Such severeplastic deformation may be accomplished by one of equiaxial channelangular processing, torsion extrusion, and twist extrusion of thenanocomposite powder.

The following example illustrates the various features and advantagesoffered by the present invention, and in no way is intended to limit theinvention thereto.

EXAMPLE 1

For the purpose of this example, the alloys Ni-20Cr and Fe-12.5Cr wereselected as the nickel-based and iron-based matrix alloy materials,respectively, for the nanocomposite, and yttrium oxide (Y₂O₃) wasselected as the reinforcing dispersoid nanoparticle.

Prototype nickel-based and iron-based metallic alloy nanocomposites werefabricated by first forming nanocomposite powders by blending −325 mesh(44 micron) of either nickel-based (Ni-20 weight percent Cr) oriron-based (Fe-12.5 weight percent Cr) alloy powder with various volumefractions (ranging from 5 to 10 volume percent) of size yttrium oxidenanopowders (particle sizes ranging from 50-100 nm). The nanocompositepowders were formed using mechanofusion, in which the yttrium oxidepowder was mechanically fused or embedded into the metal powder surface.As an alternative to blending, other procedures, such as cryomilling ormechanical alloying, can be employed to make the nanocomposite powder.The nanocomposite powder was then consolidated by enclosing thenanocomposite powder in a stainless steel can, evacuating, and sealingthe can, and extruding the can against a flat faced die at a temperatureof 1100° C. The extruded can was re-machined and hot extruded at atemperature of 1100° C. using a 9:1 reduction ratio.

The resulting as-fabricated metallic alloy nanocomposites were examinedby transmission electron microscopy (TEM) and scanning electronmicroscopy (SEM) to evaluate the respective grain sizes of the matrixand the dispersoid nanoparticles, as well as distribution of thedispersoid nanoparticles in the alloy matrix and grain boundaries. A TEMimage of an iron-based (Fe-—12.5 weight percent Cr) alloy nanocompositecontaining 5 volume percent yttrium oxide is shown in FIG. 1. Themicrostructure of the nanocomposite 100 comprises grains of metallicalloy matrix 110, ranging from about 5 microns to about 10 microns insize, and yttrium oxide nanoparticles 120, ranging from about 100 nm toabout 500 nm in size.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing description should not be deemed to be alimitation on the scope of the invention. Accordingly, variousmodifications, adaptations, and alternatives may occur to one skilled inthe art without departing from the spirit and scope of the presentinvention.

1. A structural component in a hot gas path assembly, said structuralcomponent comprising a nanocomposite, wherein said nanocompositecomprises: a) a metallic matrix; and b) a plurality of nanoparticlesdispersed throughout said metallic matrix, wherein said plurality ofnanoparticles comprises from about 4 volume percent to about 30 volumepercent of said nanocomposite.
 2. The structural component according toclaim 1, wherein said metallic matrix comprises at least one of anickel-based alloy, an iron-based alloy, and combinations thereof. 3.The structural component according to claim 2, wherein said nickel-basedalloy is one of a Ni—Cr based alloy, a Ni—Cr—Al based alloy, andcombinations thereof.
 4. The structural component according to claim 2,wherein said iron-based alloy is one of a Fe—Cr based alloy, a Fe—Cr—Albased alloy, and combinations thereof.
 5. The structural componentaccording to claim 2, wherein said hot gas path assembly is a turbineassembly.
 6. The structural component according to claim 5, wherein saidstructural component is one of a combustor, a vane, a wheel, a disc, anda casing.
 7. The structural component according to claim 1, wherein eachof said plurality of nanoparticles comprises at least one of aninorganic oxide, an inorganic carbide, an inorganic nitride, aninorganic boride, an inorganic oxycarbide, an inorganic oxynitride, aninorganic silicide, an inorganic aluminide, and combinations thereof. 8.The structural component according to claim 7, wherein said inorganicoxide is one of yttria, alumina, zirconia, hafnia, and combinationsthereof.
 9. The structural component according to claim 7, wherein saidinorganic carbide is a carbide of at least one of hafnium, tantalum,molybdenum, zirconium, niobium, chromium, titanium, tungsten, andcombinations thereof.
 10. The structural component according to claim 1,wherein each of said plurality of nanoparticles has at least onedimension, wherein said at least one dimension that is in a range fromabout 10 nm to about 500 nm.
 11. The structural component according toclaim 10, wherein said dimension that is in a range from about 10 nm toabout 30 nm.
 12. The structural component according to claim 1, whereinsaid plurality of said nanoparticles comprise from about 10 volumepercent to about 30 volume percent of said nanocomposite.
 13. Thestructural component according to claim 1, wherein said nanocompositethermally stable up to about 1200° C.
 14. A nanocomposite, saidnanocomposite comprising: a) a metallic matrix; and b) a plurality ofnanoparticles dispersed throughout said metallic matrix, wherein saidplurality of nanoparticles comprises from about 4 volume percent toabout 30 volume percent of said nanocomposite, and wherein saidnanocomposite is formed by providing a nanocomposite powder,consolidating said nanocomposite powder to form a green body, andthermomechanically processing said green body to form saidnanocomposite.
 15. The nanocomposite according to claim 14, wherein saidmetallic matrix comprises at least one of a nickel-based alloy, aniron-based alloy, and combinations thereof.
 16. The nanocompositeaccording to claim 15, wherein said nickel-based alloy is one of a Ni—Crbased alloy, a Ni—Cr—Al based alloy, and combinations thereof.
 17. Thenanocomposite according to claim 15, wherein said iron-based alloy isone of a Fe—Cr based alloy, a Fe—Cr—Al based alloy, and combinationsthereof.
 18. The nanocomposite according to claim 14, wherein each ofsaid plurality of nanoparticles comprises at least one of an inorganicoxide, an inorganic carbide, an inorganic nitride, an inorganic boride,an inorganic oxycarbide, an inorganic oxynitride, an inorganic silicide,an inorganic aluminide, and combinations thereof.
 19. The nanocompositeaccording to claim 18, wherein said inorganic oxide is one of yttria,alumina, zirconia, hafnia, and combinations thereof.
 20. Thenanocomposite according to claim 18, wherein said inorganic carbide is acarbide of at least one of hafnium, tantalum, molybdenum, zirconium,niobium, chromium, titanium, tungsten, and combinations thereof.
 21. Thenanocomposite according to claim 14, wherein each of said plurality ofnanoparticles has at least one dimension, wherein said at least onedimension is a range from about 10 nm to about 500 nm.
 22. Thenanocomposite according to claim 21, wherein said dimension is in arange from about 10 nm to about 30 nm.
 23. The nanocomposite accordingto claim 14, wherein said plurality of said nanoparticles comprise fromabout 10 volume percent to about 30 volume percent of saidnanocomposite.
 24. The nanocomposite according to claim 14, wherein saidthermomechanical process is a cryogenic milling process.
 25. Thenanocomposite according to claim 24, wherein said cryogenic millingprocess is one of a non-reactive milling process and a reactivecryogenic milling process.
 26. The nanocomposite according to claim 14,wherein said thermomechanical process comprises at least one ofextrusion, forging, rolling, and swaging of said nanocomposite.
 27. Thenanocomposite according to claim 14, wherein said severe plasticdeformation comprises equiaxial channel angular processing of saidnanocomposite.
 28. The nanocomposite according to claim 14, wherein saidsevere plastic deformation comprises at least one of torsion extrusionand twist extrusion of said nanocomposite.
 29. A structural component ina hot gas path assembly comprising a nanocomposite, wherein saidnanocomposite comprises: a) a metallic matrix, wherein said metallicmatrix comprises at least one of a nickel-based alloy, an iron-basedalloy, and combinations thereof; and b) a plurality of nanoparticlesdispersed throughout said metallic matrix, wherein said plurality ofnanoparticles comprises from about 4 volume percent to about 30 volumepercent of said nanocomposite, and wherein said nanocomposite is formedby a thermomechanical process followed by severe plastic deformation.30. The structural component according to claim 29, wherein saidnickel-based alloy is one of a Ni—Cr based alloy, a Ni—Cr—Al basedalloy, and combinations thereof.
 31. The structural component accordingto claim 29, wherein said iron-based alloy is one of a Fe—Cr basedalloy, a Fe—Cr—Al bases alloy, and combinations thereof.
 32. Thestructural component according to claim 29, wherein said hot gas pathassembly is a turbine assembly.
 33. The structural component accordingto claim 32, wherein said structural component is one of a combustor, avane, a wheel, a disc, and a casing.
 34. The structural componentaccording to claim 29, wherein each of said plurality of nanoparticlescomprises at least one of an inorganic oxide, an inorganic carbide, aninorganic nitride, an inorganic boride, an inorganic oxycarbide, aninorganic oxynitride, an inorganic silicide, an inorganic aluminide, andcombinations thereof.
 35. The structural component according to claim34, wherein said inorganic oxide is one of yttria, alumina, zirconia,hafnia, and combinations thereof.
 36. The structural component accordingto claim 35, wherein said inorganic carbide is a carbide of at least oneof hafnium, tantalum, molybdenum, zirconium, niobium, chromium,titanium, tungsten, and combinations thereof.
 37. The structuralcomponent according to claim 29, wherein each of said plurality ofnanoparticles has at least one dimension, wherein said at least onedimension is a range from about 10 nm to about 500 nm.
 38. Thestructural component according to claim 37, wherein said dimension is ina range from about 10 nm to about 30 nm.
 39. The structural componentaccording to claim 29, wherein each of said plurality of nanoparticlesis substantially spherical.
 40. The structural component according toclaim 29, wherein each of said plurality of nanoparticles has asubstantially ellipsoidal shape.
 41. The structural component accordingto claim 29, wherein said plurality of said nanoparticles comprise fromabout 10 volume percent to about 30 volume percent of saidnanocomposite.
 42. The structural component according to claim 29,wherein said nanocomposite thermally stable up to about 1200° C.
 43. Thestructural component according to claim 29, wherein saidthermomechanical process is a cryogenic milling process.
 44. Thestructural component according to claim 29, wherein said cryogenicmilling process is one of a non-reactive milling process and a reactivecryogenic milling process.
 45. The structural component according toclaim 29, wherein said thermomechanical process comprises at least oneof extrusion, forging, rolling, and swaging of said nanocomposite. 46.The structural component according to claim 29, wherein said severeplastic deformation comprises equiaxial channel angular processing ofsaid nanocomposite.
 47. The structural component according to claim 29,wherein said severe plastic deformation comprises at least one oftorsion extrusion and twist extrusion of said nanocomposite.
 48. Amethod of making a bulk nanocomposite, wherein the nanocompositecomprises a metallic matrix and a plurality of nanoparticles dispersedthroughout the metallic matrix, wherein the metallic matrix comprises atleast one of a nickel-based alloy, an iron-based alloy, and combinationsthereof, and wherein the plurality of nanoparticles comprises from about4 volume percent to about 30 volume percent of the nanocomposite, themethod comprising the steps of: a) providing a nanocomposite powder,wherein the nanocomposite powder comprises a plurality of nanoparticlesand a metallic matrix material; b) consolidating the nanocompositepowder; and c) thermomechanically processing the nanocomposite powder toform the bulk nanocomposite.
 49. The method according to claim 48,wherein the step of providing the nanocomposite powder comprises formingthe plurality of nanoparticles by at least one of mechanofusion,mechanical alloying, cryomilling, and combinations thereof.
 50. Themethod according to claim 49, wherein the step of forming the pluralityof nanoparticles comprises cryomilling the metallic matrix material toform the plurality of nanoparticles.
 51. The method according to claim50, wherein the step of cryomilling said metallic matrix materialcomprises cryomilling said metallic matrix material in a reactiveatmosphere.
 52. The method according to claim 51, wherein the reactiveatmosphere comprises at least one of nitrogen and a hydrocarbon.
 53. Themethod according to claim 48, wherein the step of consolidating thenanocomposite powder comprises pressing the nanocomposite powder to forma compact.
 54. The method according to claim 48, wherein the step ofthermomechanically processing the nanocomposite powder comprises atleast one of forging, hot-extruding, and hot-rolling, the nanocompositepowder.
 55. The method according to claim 48, wherein the step ofthermomechanically processing the nanocomposite powder comprisessubjecting the nanocomposite powder compact to severe plasticdeformation.
 56. The method according to claim 55, wherein the step ofsubjecting the nanocomposite powder compact to severe plasticdeformation comprises at least one of one of equiaxial channel angularprocessing of the nanocomposite powder, torsion extruding thenanocomposite powder, and twist extruding the nanocomposite powder.